Rotary and sliding stem valves typically including a packing to prevent leakage of process fluid past valve stems or shafts. In particular, the packing surrounds the valve stem or shaft and is typically compressed by a packing follower to ensure that an inner bore of the packing is sealed against the valve stem or shaft and that the outer surface of the packing is sealed against an opening in the valve body or bonnet assembly.
In the case of a sliding stem valve, the valve stem slides against the inner bore of the packing and, in the case of a rotary valve, the valve shaft rotates against the inner bore in the packing. In either case, the movement of the valve stem or shaft against the inner bore of the packing tends to wear the packing, which may ultimately result in leakage of process fluid past the valve stem or shaft and the packing. Although a valve packing can typically be field serviced (e.g., removed and replaced), such service usually requires time consuming and/or difficult removal of the valve actuator and/or other components from the valve because the packing follower is typically installed on and removed from the valve by sliding it over the actuator end of the valve stem or shaft.